ds18b20.lua

ds18b20.lua

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-- DS18B20 one wire module for NODEMCU
-- NODEMCU TEAM
-- LICENCE: http://opensource.org/licenses/MIT
-- TerryE  26 Mar 2017
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-- Local variables
local modname = ...

-- DS18B20 dq and default pins
local defaultPin, pin, family = 9
local DS18B20FAMILY   = 0x28
local DS1920FAMILY    = 0x10  -- and DS18S20 series
local CONVERT_T      
= 0x44
local READ_SCRATCHPAD = 0xBE

local dev_addrs, dev_hash
-- Used modules and functions
local table, string, ow, tmr, print, type, tostring = 
      table, string, ow, tmr, print, type, tostring
-- Local functions
local ow_setup, ow_search, ow_select, ow_skip, ow_read_bytes, ow_write, ow_crc8, ow_reset = 
      ow.setup, ow.search, ow.select, ow.skip, ow.read_bytes, ow.write, ow.crc8, ow.reset
local now = tmr.now
local debugPrint = function() return end
local MODE = 0

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-- Implementation
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local function init(dq, df)
  pin    = dq or pin    or defaultPin
  family = df or family or DS18B20FAMILY
end

local function enable_debug()
  debugPrint = function (...) print(now(),' ', ...) end
end

local function to_string(addr,esc)
  if type(addr) == 'string' and #addr == 8 then
    return ( esc == true and
             '"\\%u\\%u\\%u\\%u\\%u\\%u\\%u\\%u"' or
             '%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X '):format(addr:byte(1,8)) 
  else
    return tostring(addr)
  end
end

local function search_addrs()
  if not dev_addrs then
    debugPrint ("Reset Status = ", ow_reset(pin))
    ow_setup(pin)
    debugPrint ('starting search') 
    ow.reset_search(pin)
    ow.target_search(pin, family)
    local addr = ow_search(pin)
    dev_addrs, dev_hash = {}, {}

    while addr do
      debugPrint ('enter scan loop')
      if addr:byte(8) == ow_crc8(addr:sub(1,7)) then
        dev_hash[addr] = true
        dev_addrs[#dev_addrs+1] = addr
      end
      debugPrint ("search returned ", to_string(addr), (dev_hash[addr] and 'found' or 'invalid CRC'))
      addr = ow_search(pin)
      tmr.wdclr()
    end

    debugPrint ('end of scan')
    ow.depower(pin)
  end

  return dev_addrs
end

local function save_addrs()
  if not dev_addrs then search_addrs() end
  local addr_list = {}
  for i =1, #dev_addrs do addr_list[i] = to_string(dev_addrs[i], true) end
  local save_statement = 'return "ds18b20", {' .. table.concat(addr_list, ',') .. '}'
  debugPrint (save_statement)
  local save_file = file.open("ds18b20_save.lc","w")
  save_file:write(string.dump(loadstring(save_statement)))
  save_file:close()
end

local function get_addrs()
  debugPrint ("Geting Addreses")
  local s,check,a = pcall(dofile, "ds18b20_save.lc")
  if s and check == "ds18b20" then
    dev_addrs, dev_hash = a, {}
    for i = 1, #a do dev_hash[a[i]] = true end
  else
    dev_addrs = nil
    save_addrs()
  end
  debugPrint (#dev_addrs, "addreses found")
  return dev_addrs
end

local function convert_T(addr)

  if not dev_addrs then 
    get_addrs()
  end
  if addr ~= true and not dev_hash[addr] then
    debugPrint ("Unknown address ", to_string(addr))
    return nil
  end

  ow_reset(pin)
  ow_setup(pin)

  if addr == true then
    ow_skip(pin)
  else
    ow_select(pin, addr)
  end  

  ow_write(pin, CONVERT_T, MODE)
  debugPrint ("Convert issued to ", ((addr == true) and "*" or to_string(addr)))

  return true
end

local function read(addr, unit)
  if dev_addrs and dev_hash[addr] then
    ow_reset(pin)
    ow_setup(pin)
    ow_select(pin, addr)
    ow_write(pin, READ_SCRATCHPAD, MODE)
    local data = ow_read_bytes(pin,9)
    if ow_crc8(data:sub(1,8)) == data:byte(9) then
      local t = (data:byte(1) + data:byte(2) * 256)
      -- t is actually signed so process the sign bit and adjust for fractional bits
      -- the DS18B20 family has 4 fractional bits and the DS18S20s, 1 fractional bit
      t = ((t <= 32767) and t or t - 65536) * 
          ((addr:byte(1) == DS18B20FAMILY) and 625 or 5000) 

      if(unit == nil or unit == 'C') then
        t = t * 0.0001
      elseif(unit == 'F') then
        t = t * 0.00018 + 32
      elseif(unit == 'K') then
        t = t * 0.0001 + 273.15
      else
        return nil
      end

      debugPrint(to_string(addr),"data read ",to_string(data:sub(1,8)), t)
      return t
    else
      debugPrint(to_string(addr),"data read ",to_string(data:sub(1,8)), "CRC is not valid!")
    end
  else
    debugPrint(to_string(addr),"unkown address")
  end 
  return nil
end

-- Set module name as parameter of require and return module table

local M = {
  C = 'C', F = 'F', K = 'K',
  init = init, enable_debug = enable_debug, to_string = to_string,
  search_addrs = search_addrs, save_addrs = save_addrs, get_addrs = get_addrs, 
  convert_T = convert_T, read = read,
}
_G[modname or 'ds18b20'] = M
return M